Rotary hammer



W. F. TROTTER.

ROTARY HAMMER.

APPLICATION FILED JUNE 5. 1916. RENEWED 050. 4.1919.

a w M fl W47, 2 W a ya 2 2 SHEETS-SHEET Patented Jan. 25, 1921.

W.- F TROTTEB.

ROTARY HAMMER.

APPLHZAHON nun was 5, 191a. RENEWED DEC. 4. 1919.

UNITED STATES PATENT OFFICE.

WALTER F. TROTIER, Olrl CINCINNATI, OHIO.

ROTARY HAMMER.

ih fififiit Application filed June 5, 1916, Serial No. 101,792.

To all whom it may concern:

Be it known that I, lVALTEn F. Tnorrnn a citizen of the United States, residing at Cincinnati, in the county of Hamilton and tltate of @hio, have invented certain new and useful Improvements in Rotary Hammers, of which the following is a specification, reference being had therein to the accompanyinc' drawing.

This invention relates to improvements in rotary hammers. The object of the invention is to provide a structure of this class which will he composed of simple parts arranged in such way as to impart a rapidly delivered series of powerful blows with an economy of power, and which, during operation, will run steadily and smoothly, and from which will be eliminated the reactionary jars and strains that have been incident to tools of this class.

Figure 1 illustrates an implement embodying; my improvements, the parts being shown in vertical section on the plane of the line 2 2, Figw 2, parts of the motor casing being; in side elev; tiou;

9 is afront view the implement, the lower parts being in section;

3 a transverse vertical section showing the hammer, proper, and its c sing;

' e3 5, and 6 show hammers embodyimprovements but we ying from respect to the pos ;ions of the my l other in st face and tool in relation to the gove1 r' ,5 centers of the mechani m, and illusrating; successively hammers adapted to onpart blows increasing in force. Y

in the drawings there is shown a support for the operative parts, which is formed as a casing, having the upper element 1 and the lower element 6, in the chamber in the upper part 1 of the casing is placed an electric motor A. In the chamber in the lower part of the casing is mounted thehammer shaft 8. The lower part of the casing has a front wall 6, preferably integral with its cylin: drical wall; and the front end of the motor chamber is closed by a plate 1 The rear end of the lower chamber is closed by a removable plate 7. 11 is a concavo-convex facinc; plate which is securedto the front end of the support or casing with a joint at 11.

The armature shaft 3 mounted inzbearing 1 carries pinion 2 which meshes with an idle intermediate wheel 9. The latter is mounted on a shaft 10, the ends of which Specification of Letters Patent.

Patented Jan. 25, 1921.

Renewed December l, 1918. Serial No. 342,479.

are, respectively, seated in a socket in the front plate 1 of the motor chamber, and in socket in the facing plate 11. The intermediate wheel 9 meshes with a wheel 12 on shaft 8. The latter is mounted in ball bearings 6 and 7, the former being supported in the front wall 6 and the latter in the removable rear wall 7 and covered by cap 7". To the shaft 8 is rigidly secured the hammer carrier 13. it is formed with two arms or plates 13 and the weighted connecting part 18 The plates or arms 13- are fitted snugly between the hearings 6 and 7 The hammer, proper, is indicated by 14: and comprises the outer, curved, elongated, relatively wide and heavy part 14 and the inner, web-like or thinner part 1%. This web part is fitted loosely between the arms or plates 13 of the carrier and is shaped to have an arm or plate 143 extending laterally or eccentrically in one direction. The hammer is connected to the carrier by means of the pivot pin 15 which passes through the plates or arms 13 of the carrier and through the arm or plate 16 is a slot in the web part 14: of the hammer through which passes the shaft 8. This slot permits a movement of the hammer head 1% relatively to the carrier and the shaft, and around the axis of the pivot 15. The hammer is, on its outer face, formed or provided with a striking head 17 with a striking face lf in a plane tangential to a cylinder concentric with the axis of rotation, that is the axis of shaft 8 and an edge part at 17 The casing is formed with a tool-holding guide or hearing 18, and in this is fitted the tool 19. The latter can move outward when struck by the hammer, after which it can be again thrust inward, but to an extent limited by the stop 20.

Having thus specified the peculiarly shaped parts which I employ, I will call attention to the peculiar features of relative arrangement which I have designed in order to obtain the most beneficial results.

For convenience of description I shall refer to the several parts of the structure in that relationship which is shown when they are consideredas seen on a plane of section transverse to the main axis. In such a alane the point indicating the axis of the pivot 15 is located on a radius which, (from the standpoint of the direction of rotation,) is in advance of that part of the diameter which passes through the shaft axis and through the face of the striking head, and is behind or in rear of the opposite part of that diameter. I here use the term diameter as meaning the line which, passing through the axis of the shaft 8, extends to the inner circle of section of the casing in one direction, and also, in the other direction extends from that axis to said circle. This diameter includes two equal parts to each ofwhich 1 herein refer as a radius. The line 00, includes a diameter through the axis and each half of this diameter I term a fr'adius. The line y, 3 includes a diameter'passing through the main axisand through the axis of pivot 15. if is the point at the center of the main axis. 3 is the end of theradius passing through the pivot 15. I The radius if, y is in advance ofthat part of the diameter included in line 02, m (or'that radius) which passes through the striking face 17 and is behind the other part of the same diameter (that is to say, the other radius) which extends in the opposite direction toward :0, 1

The shaft and carrier rotate at a speed of from one thousand (1000) to fifteen hundred {1500) revolutions per minute. During such rotation the hammer tends to swing out, centrifugally, about the pivot. 15.

The outward movement is positively limited by the shaft 8, against which the barn.

mer is normally held by the centrifugal force. I

. The striking head 17 I locate peculiarly in relation to the center of gravity, the center of gyration, and the center ofpercussion of the hammer. For the purpose of illustration, I have indicated, diagrammatically, in the drawings, these three centers, respectively, ata, Z) and c. On the outer face of the hammer I arrange the striking head so that the point of contact with the tool at the time of imparting the blow will be at the center of percussion or will be on a line tangentatthat center to an arc struck from the axis of the shaft.

Figs. 2 and 3 the parts are so constucted and arranged that the axial plane, which includes the center of gravity a, is considerably in advance of the axial plane which intersects the striking head, and the center of percussionisoutside the periphery of the curved part of the hammer head.

In Figs. 4:, 5 and Gthe radialplane of the gravity center intersects the striking face, the center of percussion being in that face and in that plane. The inner end or anvil end of the tool '19 projects into the path of the striking head l7 a predetermined distance, which distance is relatedto the relative movementsof the hammer which re- I sultfro'm its rotatioinfrom' its rebounding,

' and from its stopping at the axis.

1 herein, at one point or another, use the terms axial plane and radial plane, and in each instance mean a plane containing the axis of the shaft 8.

As concerns the matter of rebounding, an important feature of my construction is that I hinge or locate the axis of the pivot 15 in interfere with the hammer following the natural lines of rebound after the instant of blow impact. V

The tangent from'the center of percussion 0 passes through the blow point or percussion point on the striking face 17", and this tangent'is the line of the blow to be regarded. But'the entire matter can be considered in terms of the center of gravity a. The line at i, passing tl'irough the center of gravity, can, therefore, for all intents ant purposes of explanation, be taken as being the same as the tangent referred to. And the line T-U, parallel to the striking face, can be regardedas the line containing the ainter WlllCiltiG blow is struck. If the gravity center point a is regarded as moving along the line I, and striking theline TU, it will, if free to move, rebound along the line J, and the angle of the incidence of the blow is equal to the angle of rebound;

that is to say, the angle T aT is equal to.

the angle JaU.

As shown in the drawings, the striking point is in that titer of the cycle whichis between the right hand horizontal. radius and the lowe part of the verticai diameter.

rind the pivot 15, which holds the hammer to the carrier, IS in the fourth of the cycle n advance of the one referred to. When this pivot 15 is moving through the first part of this fourth of a cycle, the hammer is held at its outermost limit by centrifugal force. But just before the pivot 15 reaches the 'horizontai diameter (as in Fig. 5), the blow is strut-hand the gravity center a is caused to travel toward the lef. The desideraturn is to have it travel on a line which is forward 01 the line 5 extendin" from the center of gravity tothe main cenof rotation and approximately radial to the axis of its pivot. Tn Fig. 5 th-isline J through the point a,'-where the center of gravity begins its rebounding movement,

and through the point a, where it terminates this movement, on a radlus through the main axis; But I have found it preferable tohave this line 5 some inciinfation to the radius through the main axis, as shown in Fig. 4 and Fig. 3; that is to say,I prefer to so positionthe parts that the line along which the center of 'grat ity'rebounds' will extend from said center to the left of the rates-so axis of shaft 8 when looking as inFigs. 2

. to 6, and will approximate a radial position relative to the axis of its pivot 15 shown in dotted lines, Fig. 4. This relieves the machine from the stresses incidental to starting the hammer on its forward movement while it is moving in a direction opposite to the direction of rotation. In connection with this rebounding of the hammer, it is to be noticed that, during this movement, the striking head 17 smoothly and easily escapes from the anvil end of the tool. The rounded corner and the edge 17 of the striking head are so designed as to provide for this easy escape of the striker, although a severe blow has been struck the previous instant.

The rebounding continues until the lower end of the slot 16 comes to the center stop (in this case, the shaft 8), this occurring at the time the striking head 17 is at its innermost position, as aforesaid, far enough to permit it to pass the tool.

The dotted lines indicate the position which the hammer takes at the termination of its rebounding, the pivot 15, at that instant, having been moved from the full line positions to those in dotted lines.

I do not mean to be understood as saying that all the advantageous features are dependent upon having the lines of rebound of the hammer such that the center of gravity will rebound on a line extending from said center to the left of the axis of shaft 8 when looking as in Figs. 2 to 6. Under some circumstances, I may sacrifice some of the matters above described and arrange the parts as shown in Fig. 6. Here the parts are so constructed and related that the horizontal line through the center of gravity a, parallel to the striking face, is relatively so elevated as to-include' or approximate the axis ofthe pivot 15, the latter being set relatively lower than that in the constructions in Figs. 4 and 5, and the axial plane through the pivot 15 being at a greater angle to the plane through the center of gravity. The blow, struck when the center of gravity is traveling on the line 1, causes the center of gravity to rebound. along the line J (Fig. 6), which extends from the center of gravity along the line at the right of the main axis when looking as in Fig. 6. It will be seen that a distinct effort must be exerted at the pivot and energy must be consumed to overcome the inertia of the hammer, when comparison is made with the actions of the de vices in Figs. 6 and 5; the energy of rebound with the parts in Fig. 6, having a negative effect on the forward motion of the mechanism. These matters are fully illustrated in the comparative views, Figs. 4, 5 and 6. Inferior results are attained when the parts are constructed and arranged as in Figs. 5 and 6 in comparison with the construction and arrangement in Fi 4. However, there are other features of ac vanta'ge incident to such constructions as'that in Fig. 6, such as the disposition of the hanr mer metal in relation to the "striking face, the anode of pivoting, and the stopping at the axis.

The striking face can be located in the radial plane of the center of gravity or in the rear of that plane, provided the face'is intersected by a tangent through the center of percussion. The center of: gravity is positioned in an axial plane bisecting the hammer head. That is to say, the amount of hammer head metal in advance of the axial plane of the center of gravity is approxi-' mately equal to the amount in the rear of that plane. If the striking face is in the ra dial plane of the'center of gravity, as in Fig. 5 and others, there is substantially as muchhammer head metal in front of the impact point as there is behind it. It has been customary in making rotary hammer mechanisms to so arrange. the hammers as to have their hitting faces forward of the gravity centers. But'l have found, upon carefulinvestigation, that it is impossible, with parts so made and arranged, to get the results that I attain, and particularly with small compacttools, where I position a. large part of the metal of the hammer head forward and a large part in the rear of the striking face. With respect to the use of the central shaft as a device for limiting the swinging movements of the hammer, it is to be noted that a stop for this purpose either "must be stationary or must be one that will rotate in the same direction with the hammer but at a much slower speed. I employs is stationary and located at the central axisof the machine. It need not be a body extending continuously across the center, as shown. It may be composed of one or more stops on the frame, provided they are arranged at the axis. 4

onsidering the mechanism shown as'a specific form of embodiment "of the invention, there are numerous important features of advantage incident to it. The hammer casing is completely inclosed. The interior chamber is cylindrical and unobstructed, and the hammer structure has only the two elements, which are closely centered and compactly arranged. One is the. carrier element having the peripherally expanded momentum weight, and the other is the hammer element which counterbalances the weight element 13*, the hammer having the elongated curvilinear head which is placed diametrically opposite to the'weight part, the two being arranged to provide an approximately cylindrical mass which maintains a uniformity of rotation, even at high speed, and without jolting or jarring any The stop which of the shafts or bearings. In addition to the advantages above described, as incident to the relative arrangement of the pivot 15, is the fact that, being close to the weight metal, it leaves a lar e part of the cylindrical space availiable for a hammer structure of a short radius and which, though in a small chamber, is relatively large and heavy.

What I claim is:

1. A. rotary swing hammer having a hammer head pivoted. on an axis parallel to the axis of rotation and formed with astriking face in a plane tangential to a cylinder around the axis of rotation and arranged to be intersected by the plane including the axis of rotation and the center of gravity.

2. A rotary hammer having a hammer head pivoted on an axis of rotation and ermed with a striking face in a plane which includes the center of percussion and is tangential to a cylinder around the axis of rotation, the head having its center of gravity and the said center of percussion in a tum weight on one side or" the axis of rota! tion, and the centrifugally moving hammer having an elongated curvilinear head approximately concentric with the axis of rotation and arranged diametrically opposite tosaid momentum weight and having also a pivoted arm and a slot in saidarm to provide stops, a stationary stop at the axis of rotation to engage the stops pro- I vided by the slot.

5. The combination o1 thecasinghaving a tool support, the rotary carrier in the casing having a momentum weight on one side of the axis of rotation and a swinging hammer pivoted to the carrier and formed with an elongated curved head. diametrically opposite to the momentum weight, and a pivot arm for the hammer hinged to the carrier at points near the momentum weight and having a projection extending outward from and between the ends of the curved head, which projection is provided with a striking face in a plane tangential to a cylinder around the axis of rotation.

G. A. rotary hammer having a hammer head rotating around a fixed axis and pivoted on a rotating axis parallel to the axis of'rotation, and formed with a striking lace, through which passes the plane that includes the center of gyration and the cen ter of gravity of the head.

7. A rotary hammer having a hammer head rotating around a fixed axis and vibratable around an axis which rotates irou.-d said fixed axis, said head hav'ng a tr'king face int rsected by the plane which ncludes the center of percussion, the center of gyration and the center of gravity.

8. A rotary hammer having a hammer head rotating around a fixed axis and vibrating on an axis which rotates around said fixed axis, said hammer head having a striking face intersected by the plane which includes the center of gravity, the center of percussion and also, at the instant of the stroke, includes said fixed axis.

9. A rotary hammer having a hammer head rotating bodily around a fixed axis of rotation and movable relatively tosaid axis and formed with a striking face in a plane having one or more or its lines'included in the plane, which also includes the center of percussion and the center of gravity ofthe mass of the hammer head.

In testimony whereoi I aflix my signature in presence of two witnesses. Y

- WAL'lElSL F. TROTTER. Witnesses:

EMMA L. BAUER. J OHN DONNELLY. 

